HIGHLIGHTS AND FOLLOW UPS from the IX International Scientific Congress on Fur Animal Production, Halifax 2008 Prepared by Professor Georgia Mason, Ontario Agricultural College, University of Guelph
# 2: The Behaviour and Welfare of Fur Animals, with a Focus on Mink Behaviour and welfare were covered in a half-­‐day session at the congress, with a mix of spoken and poster presentations. Most (9/12) of these were on mink, along with one on chinchillas, one on raccoon dogs, and one on silver foxes. This summary will review the presentations focusing on mink and how well they adapt to ‘cage life’ – covering both the relevant presentations from this session as well as one additional paper in the ‘Management’ session on group housing. This summary will also use more recent research to show what has been published or found out on these topics in the 18 months since the IFASA congress. Small barren cages as a potential welfare (and ‘PR’) concern Mink cages provide far more scope for movement and relative space than do typical North American farm conditions for pigs, chickens or dairy cows: mink can turn around, climb and run; choose between two discrete areas – their nestbox and the open cage; and are largely kept out of contact with their manure. This contrasts favourably with the normal conditions of most intensively-­‐farmed food animals.1 However, the average mink cage is not perfect from a welfare perspective, the most conspicuous on-­‐farm evidence of problems being ‘stereotypic behaviour’. The clock-­‐work-­‐like pacing, head-­‐twirling and bobbing of farmed mink is a common sight, especially in the daily run-­‐up towards feeding. Across a range of species and husbandry systems, these predictable, repetitive behaviours are statistically associated with environments that induce physiological stress hormone responses, or that animals would avoid if they had the choice.2 The stereotypic behaviours of farmed mink are no more common or severe than those of many other farm, laboratory or zoo animals – indeed they are often less common and severe. However, given the intense scrutiny and criticism that fur farming often attracts, it makes sense to see if cage environments for mink can be improved.1 Improving welfare and reducing stress could have practical benefits to farmers too: NSAC student Jennifer Dobson has found that the kits of stressed dams grow more slowly3, and across a range of other species we know that reducing stress boosts immune function and fertility, and reduces anxiety and aggression.1 Adapt mink to better suit their cages, or adapt cages to better suit the mink? Genetic selection, as every farmer knows, is a powerful tool for improving productivity. It also offers huge scope for improving welfare, by accelerating domestication and leading to animals that are better adapted, behaviourally and temperamentally, to farm conditions. For example, a recent Finnish study indicates that swimming – an important behaviour to mink in the wild – has a genetic component, suggesting that when unwanted, frustrated motivations to perform this natural behaviour occur in farmed animals, they can be reduced by selection.4 Furthermore, a large body of impressive Danish research over the last decade shows that fear of humans, corticosteroid stress hormone outputs, and stereotypic behaviour can all be reduced in farmed mink via genetic selection. However, as a detailed Danish study published early this year shows5, even though selecting against stereotypic behaviour rather effectively reduces it, doing so increases inactivity and so brings with it risks of weight gain (with negative consequences for litter size)5,6,7; and in some populations it may also increase levels of fearfulness, too5. So, while on-­‐going genetic work continues wrestling with the knotty problem of how best to adapt mink to standard cages, other researchers instead have taken a complementary approach to improving mink welfare, examining how husbandry (especially cage environments) could be altered. This work builds on many studies on diverse species all showing that more complex, ‘enriched’ cages reduce stress and abnormal behaviour. This work also builds on experiments showing that if mink are allowed to perform ‘work’ in order to reach enrichments from their standard farm cages, they will do so – vigorously pressing levers that allow them to use a running wheel8, for example, and pushing heavily-­‐
weighted doors to reach a range of enrichments including cat toys, plastic objects to chew, plastic tunnels, and bowls or baths full of water.9 So, if farmed mink want ‘more to do’, would allowing this improve their welfare? And can this be done this in a practical, cost effective way? What can we learn from experimental ‘super-­enriched’ cages? ‘Super-­‐enriched’ cages are the type of experimental, non-­‐commercial cage that make farmers reel in horror. These may offer a dazzling variety of different enrichments (which could well be expensive and time-­‐consuming to provide, and also difficult to maintain); involve impractical enrichments (like water-­‐baths animals can dive in, circulating filtered water in which they can wade and ‘head-­‐
dip’, or purpose-­‐built running wheels); and/or use enclosures six times or more the size of a typical farm cage e.g. 1,4,9,10 Three such set-­‐ups were presented at the IFASA meeting. Steffen Hansen from Denmark showed how typical mink stereotypies disappear in animals supplied with running wheels, being completely replaced by wheel-­‐running11. Subsequent analyses showed that providing the wheels did not reduce output of the stress/activity hormone cortisol 2, but this could be because the enriched animals were so very active. A Swedish PhD project conducted by Helene Axelsson (nee Lindberg) and supervised by Lena Lidfors, included a study of very large cages, super-­‐enriched with various objects and a water-­‐bath, on 10 month old silver-­‐blue females10. Stereotypic behaviour was reduced from 10.4% of the animals’ active time, to just 1.4%; and was replaced by active rather than inactive behaviour, so potentially reducing risks of unwanted weight increases. Finally, myself and PhD student Maria Diez have worked with very large super-­‐enriched cages at Michigan State University, in collaboration with Steve Bursian1. We had few results at the time of the IFASA meeting, but in the 18 months since have found that the super-­‐enriched cages cause small but statistically significant increases in body size, relative brain size and relative spleen size; make males more attractive to females (females copulate more often and for longer with enriched-­‐raised males); reduce output of the stress/activity hormone cortisol by c. 30%; and dramatically reduce stereotypic behaviour by about 80%, from 13.8% time to 2.9% time (again, without increasing inactivity in females, although enriched males do become more slothful). These studies give ‘benchmark standards’ for evaluating the effectiveness of more practical enrichments (see next section); and also suggest that enrichments might have the potential to improve not just welfare, but also reproductive output – though direct tests of this idea are now needed. They also made me wonder if farms of the distant future, when gas and oil have run out, might use running wheels and ‘mink power’ to generate electricity! On a more down-­‐beat note, these and other similar studies occasionally highlight the dangers or person-­‐hours associated with some enrichments (e.g. enrichments that are rapidly chewed and destroyed need frequent replacement; and mink may risk strangling themselves with inappropriately-­‐presented ropes); and they also demonstrate that the most effective enrichments can vary between countries (e.g. swimming water reduced stereotypic behaviour in a Finnish project4, but not in Danish or Dutch studies13) – suggesting that enrichments may need tailoring to the genetics of local populations. Practical enrichments for standard farm cages Can more practical additions to standard cages yield the benefits of ‘super-­‐enrichment’? In my IFASA talk1, I presented an inspiring success story from Denmark 14. Steffen Hansen and colleagues raised kits (brown ‘Wildtype’) from birth until the pelting season in enriched farm cages; and after males were pelted, females remained in these cages until mating. The enrichments consisted of standard cages supplied with a plastic cylinder and a wire cylinder, each suspended from the cage ceiling to provide new resting places; two table tennis balls; and two pieces of rope which the animals chewed. Kit growth was not affected, but young adult females loss less body weight during slimming, if enriched between December and March (whether this had negative effects on reproduction was not reported, but none were said to be overly conditioned). This ‘body weight effect’ probably reflected the females’ dramatically lower stereotypic behaviour (reduced by about 75% compared to standard-­‐housed mink). Cortisol output was also reduced by c. 30%. In addition, the enriched animals were less likely to chew fur off their tails. In contrast, simply doubling the animals’ cage size without supplying enrichments had no such effects (see18 for similar findings). Swedish researchers Lidfors and Axelsson conducted similar experiments on two commercial farms, using black-­‐cross adult females that had previously lived in standard unenriched cages11,15. Animals were supplied with a wire mesh shelf, a plastic cylinder, or a ball – or all three combined. The minks’ behaviour was observed between December and April. On one farm, these enrichments had no effects. On the other farm, however, simply providing a wire shelf successfully reduced stereotypic behaviour from c10% of time to approximately zero (while, rather strangely, supplying all three enrichments did not)10,15. These three studies show that simple, practical enrichments can potentially yield benefits rivaling those of the impractical ‘super-­‐enrichments’ of the previous section. However, it is also clear they do not always do so. Possible reasons for this variation include the age at which mink are first supplied with enrichments; genetic differences between populations; other differences between farms (e.g. levels of human disturbance); and subtle differences between the enrichments supplied.* Group-­ and family-­housing systems: could unnatural social systems be enriching? Leaving a whole litter together until pelting, in inter-­‐connected standard cages or doubled-­‐up cages ‘stacked’ on top of each other, is a relatively new system that has caused some controversy over the last decade or more. Danish research e.g. 16 generally finds that such systems elevate aggression, cause bitemarks and even increase mortality; while Dutch farmers defend the system, arguing that these problems are minimal, and pointing to reduced stereotypic behaviour (and greater economic efficiency). Three presentations at the IFASA congress discussed group housing. Jan de Rond and Gerrit de Jonge showed Dutch data from 15 years’ work with brown ‘Wildtype’ mink at the Spelderholt research farm17, sometimes from groups as large as 17 mink in several interconnected cages. The * To illustrate, all balls may not be created equal for farmed mink. Danish mink supplied with small, smooth table tennis balls were never observed using them14; but Swedish mink given 8cm wide balls with a more rubbery, textured surface often took them into their nest-­‐boxes15, and our Michigan State Uni. mink often carry about the ‘waffle balls’ [golf practice balls] provided to them1. •
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researchers reviewed evidence of reduced stereotypic activity and well-­‐priced, larger pelts (though when this work was first started in the mid ‘90s, group-­‐housed mink did have more bitemarks). Mink also generally slept together, all huddling in one nestbox even when several other boxes were free. More recently, a team working in Sweden18 found no increase in bitemarks on the leather side of the pelt even at the highest stocking density they used (two male and two female kits in a double-­‐
height stacked cage). PhD student Sari Hanninen and her supervisors in Finland, however, found that the ‘general impression’ of pelts from group-­‐housed mink was worse at auction19. In papers published since the congress, they further report more scars on the pelts of group-­‐housed female mink, though also less stereotypic behaviour, while alive, in both sexes 20 (with cortisol levels unaffected)20. In a variant of group housing where the dam is left with the litter until 6 mos. of age (‘family housing’), the Finnish team then found that cortisol levels were lower in family-­‐housed than conventionally-­‐housed mink – but again such animals also showed more evidence of aggression, with more bite scars 21. Overall, some thus argue that the social interactions of grouped juvenile mink are enriching, with the reduction in stereotypic behaviour supporting this view. It does seem likely that for the ‘average mink’, and with the system working well, group-­‐housing can benefit welfare. However, whether this is true for all mink – particularly subordinate animals in the group – is far more questionable, and it is also clear that when this system goes wrong (e.g. with escalated aggression, or infected bite-­‐wounds) it can go very wrong indeed. Whether these welfare costs to the mink are outweighed by the benefits seems likely to depend on the colour-­‐type; selection for low aggression within these new systems; stocking density; feed levels, frequency, and number of feeding sites; and importantly, the skill and stockmanship of the farmer. Take home messages Mink welfare problems are fewer than many intensively-­‐housed species, but should not be overlooked (not least because fur-­‐farming attracts more criticism than other industries). Stereotypic behaviour (e.g repetitive pacing, circling and head-­‐bobbing in mink) is generally regarded as a sign of relatively poor housing conditions. However, attempts to reduce it via e.g. genetic selection should not make mink too inactive – since inactivity brings with it its own welfare, health and reproductive problems. Simple in-­‐cage enrichments can potentially be very effective, reducing stereotypic behaviours and stress hormone levels as effectively as more elaborate, impressive (and impractical) systems; these include balls, wire mesh cylinders, raised shelves and chewing ropes. Doubling cage sizes, in contrast, seems to have minimal effects. However, which simple enrichments work best practically and from a welfare perspective seems to vary from study to study (perhaps due to local genetics; cage size which determines how much enrichment can be added; and subtle properties of the enrichments themselves, e.g. the size and material of balls). Socially-­‐housing mink (raising kits in groups or even leaving them with their mothers until 6 mos.), can potentially reduce stereotypic behaviour; but it brings with it risks of aggression. Most welfare problems in mink can probably be effectively tackled by farmers, for example via improved cage design and genetic selection. References
1. Mason, G. (2008). Why should environmental enrichment be used to improve welfare on mink farms?
IFASA congress.
2. G. J. Mason & N. Latham (2004). Can’t stop, won’t stop: Is stereotypy a reliable animal welfare indicator?
Animal Welfare 13: S57 – S 69.
3. Dobson, J., Mason, G. & Rouvinen-Watt, K. (2008). Intensive handling of mink (Neovison vison) during
lactation reduces litter performance and weaning weight. IFASA congress.
4. Mononen, J., Mohaibes, M., Savolainen, S. & Ahola, L. (2008). Water baths for farmed mink: Intraindividual consistency and inter-individual variation in swimming water and effects on stereotyped behaviour.
Agricultural and Food Science 17, 41-52.
5. Hansen, B. K., Jeppesen, L. L. & Berg, P. (2010). Stereotypic behaviour in farm mink (Neovison vison) can
be reduced by selection. Journal of Animal Breeding and Genetics, 127, 64-73.
6. Baekgaard, L. P. F & Sonderup, M. (2008). Female body condition and early kit mortality: a description
from practice. IFASA congress.
7. Meagher, R. & Mason, G. J. (2008). Does inactivity in the nestbox predict poor reproductive performance
in mink? IFASA congress.
8. SW Hansen, MB Jensen (2006). Quantitative evaluation of the motivation to access a running wheel or a
water bath in farmed mink. Applied Animal Behaviour Science 98, 127-144
9. G. Mason, J. Cooper & C. Clarebrough (2001) The welfare of fur-farmed mink. Nature 410: 35 – 36.
10. Lidfors, L., Lindberg, H. & Alden, E. (2008). The effect of environmental enrichment on farm mink in
Sweden. IFASA congress.
11. Hansen, S. W. & Damgaard, B. M. (2008). Running in a running wheel substitutes for stereotypies in mink
(Mustela vison) but does it improve their welfare? IFASA congress.
12. Hansen, S. W. & Damgaard, B. M. (2009). Running in a running wheel substitutes for stereotypies in mink
(Mustela vison) but does it improve their welfare? Applied Animal Behaviour Science 118, 76-83.
13. Vinke, C.M. Hansen, S.W. Mononen, J. Korhonen, H. Cooper, J.J. Mohaibes, M. Bakken, M. &Spruijt,
B.M. (2008). To swim or not to swim: An interpretation of farmed mink's motivation for a water bath. Applied
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14. Hansen, S. W., Malmkvist, J., Palme, R. & Damgaard, B. M. (2007). Do double-cages and access to
occupational materials improve the welfare of farmed mink? Animal Welfare 16, 63-76.
15. Axelsson, H. M. K., Alden, E. & Lidfors, L. (2009). Behaviour in female mink in enriched standard cages
during winter. Applied Animal Behaviour Science 121, 222-229.
16. Pedersen, V., Jeppesen, L. L. & Jeppesen, N. (2004). Effects of group housing on behaviour and production
performance in farmed juvnile ink (Mustela vison). Applied Animal Behaviour Science 88, 89-100.
17. De Rond, J. & de Jonge, G. (2008). Group housing of mink in flat and climbing cages. IFASA congress.
18. Lindberg, H., Alden, E., Hansen, S. W. & Lidfors, L. (2008). Effects of climbing cage and feeding strategy
on behaviour and production in farmed mink. IFASA congress.
19. Hanninen, S., Polonen, I., Lahti, M., Pyykonen, T. & Ahola, L. (2008). Group housing of juvenile mink:
effects on pelt length, general impression and price. IFASA congress.
20. Hanninen, S., Ahola, L. Pyykonen, T. Korhonen, H. T., & Mononen, J. (2008). Group housing in row
cages: an alternative housing system for juvenile mink. Animal 2, 1809-1817.
21. Hanninen, S., Mononen, J., Harjunpaa, S., Pyykonen, T., Sepponen, J., & Ahola, L. (2008). Effect of family
housing on some behavioural and physiological parametes of juvenile farmed mink (Mustela vison). Applied
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